<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>for循环</title>
</head>

<body>
  <script>
    let sum = 0
    for (let i = 1; i <= 100; i++) {
      if (i % 2 === 0) {
        sum += i
      }
    }
    document.write(sum)
  </script>
</body>

</html>